•  During the century leading up to this controversy (which occurred shortly after 1700), the concept of “substance” was of central importance in philosophy, especially in continental Europe (as opposed to Great Britain). And the key criterion for being a substance (as opposed to being a “mode” of a substance) was the possibility of independent existence. So, when Leibniz claimed that space did not exist independently of the objects in it (see Okasha, p. 96), he was claiming that space was not a “substance” in this sense. Although the concept of substance no longer has quite the same meaning and importance, a form of the idea of absolute space still survives today (see Okasha, p. 103), and it is often referred to as “spacetime substantivalism.”

•  The person most closely associated with the rejection of Newton’s idea that the bucket experiment would have the same results in the absence of other objects (see Okasha, pp. 101f) is the physicist Ernst Mach (1838-1916), who I have mentioned before as an example of a positivist. Mach held a relational view of space and quite explicitly attributed the result of the bucket experiment to the rotation of the bucket relative to the fixed stars. Einstein is known to have been influenced by Mach’s ideas, and that’s probably one of the reasons—though there are many others, too—that people have often associated that Einstein’s theory of gravitation (i.e., general relativity) with a relational view of space.

•  The dispute Okasha describes was not carried out between Newton and Leibniz directly. The arguments that Okasha cites from Newton appear in his Principia (at the end of the Scholium to the definitions, just before he states his laws of motion)—at pp. 15-18 in the 18th century translation from the Latin on line at

http://books.google.com/books?id=Tm0FAAAAQAAJ

Leibniz’s arguments are found in a series of letters between Leibniz and Samuel Clarke (1675-1729) in the last year of Leibniz’s life (1715-16). Clarke was a disciple of Newton, and it is generally assumed that Newton was the source for most of the arguments that he offered. Clarke published the correspondence after Leibniz’s death, and you can see it on line in its original form at

http://books.google.com/books?id=_RUHAAAAQAAJ

A variety of issues are addressed, but Leibniz’s arguments against absolute space begin to appear in ¶5 of his third letter, at p. 57 in this edition. (You will find French and English on alternate pages in the correspondence since Leibniz, although German, worked primarily in Latin and French. Also, if you are not used to reading printing from that era, note that in many cases the letter ‘s’ will be written as the “long s,” a letter ( ſ ) that looks like the letter ‘f’ without the full cross bar.)